In this paper, a temperature controlled UV-laser lithographic method for the fabrication of integrated-optical polymeric waveguides is presented. The fabricated integrated-optical polymeric waveguides are examined at different processing temperatures. The influence of the temperature on the refractive index depth distribution and thus on the mode field distribution, the number of modes and the effective refractive index of each mode, respectively, is investigated. The refractive index depth profile of the integrated-optical polymeric waveguides is examined by using the Mach-Zehnder interferometric method and an image processing technique. The interference phase differences are extracted in order to determine the refractive index depth profiles of the fabricated optical waveguides. After determining the refractive index depth distribution experimentally, the data of the refractive index depth distribution are employed to calculate the mode field distribution, mode numbers and the effective refractive indices.